In a three-dimensional reconstruction method called DFF (Depth From Focus), several images of a scene are taken with an image acquisition device, each time shifting the maximum sharpness plane along the image acquisition axis between the images, without moving the elements of the scene between the image acquisitions. By next combining the sharp regions of the different captured images, it is possible to reconstruct the three-dimensional relief of the scene, plane by plane.
In another three-dimensional reconstruction method called DFD (Depth From Defocus), the relief of the scene is reconstructed by analysis of the optical unsharpness level in the images. In each image, the higher the unsharpness level of a zone is, the more it is shifted depthwise relative to the sharpness zone. By knowing the optical parameters of the image acquisition device, it is possible to determine the depth of the point of the scene associated with each pixel of the image.
The optical unsharpness level in an image is for example measured by measuring the contrast in the image. A low contrast indicates a fuzzy region of the image, while a high contrast indicates a sharp region of the image.
It is possible to project a textured light pattern on the scene that increases the contrast to improve the precision of the analysis of the optical unsharpness in the captured images. The light pattern for example comprises parallel lines, fringes or a checkerboard.
Nevertheless, this is not fully satisfactory in terms of precision, for example for the three-dimensional reconstruction of surfaces with a low roughness.